Growth and metal uptake of edamame [Glycine max (L.) Merr.] on soil amended with biosolids and gypsum

ABSTRACT

Although biosolids are a rich source of plant nutrients, there is concern about the potential heavy metal uptake by crops grown on biosolid-amended soils. This study was conducted to determine the effects of limed or composted biosolids and flue gas desulfurization gypsum (FGDG) on edamame growth, nodule development, and metal uptake. Two consecutive crops of edamame were grown on 40 and 80 T ha^?1 biosolid-amended soil with and without 10 T ha^?1 FGDG. Biosolids with or without FGDG did not reduce biomass, nodules, or grain yields in the first harvest and increased yields of all three tissues in the second harvest. Lead and cadmium concentrations in grain and biomass were below the instrument detection limits. Copper, manganese, and zinc were within the ranges normally found in soybean grain. In this pot study, biosolids and FGDG did not reduce edamame growth or increase grain metal concentrations to levels of concern.     

Suitability of inorganic and organic amendments for in situ immobilization of Cd,Cu, and Zn in a strongly contaminated Kastanozem of the Mashavera valley,SE Georgia. I. Effect of amendments on metal mobility and microbial activity in soil

The aim was to find an adequate, cost‐efficient in situ remediation technique for the Mashavera valley, a mining area in SE Georgia heavily contaminated with Cd, Cu, and Zn. A 12‐month experiment was conducted to test: iron grit, natural zeolite, biochar, and Divergan® (a scavenger) for soil melioration. The amendments were added in different concentrations to the topsoil of a Kastanozem. Mobile metal concentrations decreased with increasing concentrations of amendments in the sequence Divergan® >> iron grit ≈ natural zeolite > biochar. In the same order amendments enhanced activities of soil microbial respiration, alkaline phosphatase, and dehydrogenase; microbial C also followed this trend. A sequential extraction confirmed a shift from easily mobilized to heavily bound fractions. The addition of 2% (w/w) of Divergan® was sufficient to lower mobile trace metal concentrations below German thresholds by chemisorption, and soil microbial activity was significantly increased. The effects of all other treatments were at a much lower level and not found suitable due to needed application rates.     

Heavy‐metal mobilization and uptake by mycorrhizal and nonmycorrhizal willows (Salix × dasyclados)

Ectomycorrhizal fungi have been shown to affect metal transfer from the soil to the host plant, but the use of these fungi for increased phytoextraction of heavy metals has been scarcely investigated. Therefore, a two‐factorial pot experiment was conducted with Salix × dasyclados and (1) two contaminated soils with different concentrations of NH₄NO₃‐extractable metals and (2) two strains of the ectomycorrhizal fungus Paxillus involutus (one strain originating from a noncontaminated site—Pax1, and another from a contaminated site—Pax2). The inoculation with Pax2 increased the phytoavailability of Cd in the soils. Inoculation with both fungal strains increased the stem and root biomass, but had no effect on metal concentrations in the stems. Decreased Cd and increased Cu concentrations were observed in the roots of inoculated willows. The inoculation with P. involutus increased Cd (up to 22%), Zn (up to 48%), and Cu content in the stems. Decreased Pb content (Cu and Pb content were always <1 mg per plant) occurred in the stems from plants at the soil with the higher concentration of NH₄NO₃‐extractable metals. Contrary to this, in the soil with lower concentrations of NH₄NO₃‐extractable metals, the inoculation had no significant effects on the total uptake of Zn and Cu and even caused decreased Cd (Pax2) and Pb (Pax1) contents in the stems. Strain Pax2 had higher colonization densities, but the plants had lower mycorrhizal dependencies in the contaminated soils than after inoculation with the strain Pax1. Generally, metal extractability in the soils substantially affected the mycorrhizal dependency and heavy‐metal uptake of the willows. We concluded, that the inoculation with P. involutus offers an opportunity to particularly increase the phytoextraction of Zn, but the metal extractability and fungal strain effects have to be tested.     

Spatial distribution of soil heavy metal concentrations as indicator of pollution sources at Mount Križna (Great Fatra,central Slovakia)

The objective of this study was to test the suitability of a simple approach to identify the direction from where airborne heavy metals reach the study area as indication of their sources. We examined the distribution of heavy metals in soil profiles and along differently exposed transects. Samples were taken from 10 soils derived from the same parent material along N-, S-, and SE-exposed transects at 0—10, 10—20, and 20—40 cm depth and analyzed for total Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn concentrations. The heavy metal concentrations at 0—10 cm were larger than background concentrations in German arable soils except for Cr (Cd: 0.6—1.8 mg kg^—1; Cr: 39—67; Cu: 40—77; Ni: 87—156; Pb: 48—94; Zn: 71—129; Fe: 26—34 g kg^—1; Mn: 1.1—2.4). Decreasing Cd, Cu, Mn, and Pb concentrations with increasing soil depth pointed at atmospheric inputs. Aluminum and Ni concentrations increased with soil depth. Those of Fe, Cr, and Zn did not change with depth indicating that inputs at most equalled leaching losses. The Pb accumulation in the surface layer (i.e. the ratio between the Pb concentrations at 0—10 to those at 20—40 cm depth) was most pronounced at N-exposed sites; Pb obviously reached Mount Križna mainly by long-range transport from N where several industrial agglomerations are located. Substantial Cd, Cu, and Mn accumulations at the S- and SE-exposed sites indicated local sources such as mining near to the study area which probably are also the reason for slight Cr and Zn accumulations in the SE-exposed soils. Based on a principal component analysis of the total concentrations in the topsoils four metal groups may be distinguished: 1. Cr, Ni, Zn; 2. Mn, Cd; 3. Pb (positive loading), Cu (negative loading); 4. Al, Fe, indicating common sources and distribution patterns. The results demonstrate that the spatial distribution of soil heavy metal concentrations can be used as indication of the location of pollution sources.     

Effects of soil water content on growth,tillering, and manganese uptake of lowland rice grown in the water‐saving ground‐cover rice‐production system (GCRPS)

A 2‐year field experiment and a pot experiment were carried out to compare Mn uptake, tillering, and plant growth of lowland rice grown under different soil water conditions in the ground‐cover rice‐production system (GCRPS) in Beijing, North China. The field experiment was conducted in 2001 and 2002, including two treatments: lowland‐rice variety (Oryza sativa L. spp. japonica) grown under thin (14 μm) plastic‐film soil cover (GCRPS_plastic) at 80%–90% water‐holding capacity (WHC) and traditional lowland rice (paddy control) grown with 3 cm standing‐water table. The pot experiment was conducted in a greenhouse with four treatments: (1) traditional lowland rice: paddy control; (2) GCRPS, water‐saturated soil: GCRPS_saturated; (3) GCRPS at 90% water‐holding capacity (WHC): GCRPS_90%WHC; and (4) GCRPS at 70% WHC: GCRPS_70%WHC. Results of the field experiment showed that dry‐matter production, number of tillers, as well as N and Mn concentrations in rice shoots of GCRPS were significantly lower than in paddy control, while there was no significant difference in shoot Fe, Cu, Zn, and P concentration and nematode populations. In the pot experiment, shoot Mn concentration significantly decreased with decreasing soil water content, while soil redox potential increased. Shoot–dry matter production and tiller number of GCRPS_saturated were significantly higher than in other treatments. Significant correlations were observed between the shoot Mn concentration and tiller number at maximum tillering stage in the field and pot experiment, respectively. We therefore conclude that the limitation of Mn acquisition might contribute to the growth and yield reduction of lowland rice grown in GCRPS. The experiment provides evidence that GCRPS_plastic combined with nearly water‐saturated soil conditions helps saving water and achieving optimum crop development without visual or latent Mn deficiency as observed under more aerobic conditions.